Multiple Choice
Which of the following best describes how to calculate the percent by mass of each element in a compound?
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3. Chemical Reactions
Mass Percent
Multiple Choice
What is the mass percent of aluminum in the compound Al2O3?
A
60.0%
B
47.1%
C
35.0%
D
52.9%
Verified step by step guidance1
Identify the chemical formula of the compound, which is Al\_2O\_3, meaning it contains 2 aluminum (Al) atoms and 3 oxygen (O) atoms per formula unit.
Find the atomic masses of aluminum and oxygen from the periodic table: aluminum (Al) has an atomic mass of approximately 26.98 g/mol, and oxygen (O) has an atomic mass of approximately 16.00 g/mol.
Calculate the molar mass of the compound by summing the total mass contributed by aluminum and oxygen: \( \text{Molar mass} = 2 \times 26.98 + 3 \times 16.00 \) g/mol.
Calculate the total mass of aluminum in one mole of the compound: \( \text{Mass of Al} = 2 \times 26.98 \) g.
Determine the mass percent of aluminum by dividing the total mass of aluminum by the molar mass of the compound and multiplying by 100: \( \text{Mass \% Al} = \frac{2 \times 26.98}{\text{Molar mass of Al\_2O\_3}} \times 100 \).
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